当按下按键时运行脚本 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <script>
    function displayResult() {
      var x;
      if (window.event) // IE8 及更早IE版本
      {
        x = event.keyCode;
      } else if (event.which) // IE9/Firefox/Chrome/Opera/Safari
      {
        x = event.which;
      }
      var keychar = String.fromCharCode(x);
      alert("按键 " + keychar + " 被按下");
    }
  </script>
</head>
<body>

  <p>当用户在输入域按下按键时触发函数。 该功能提醒按下的键。</p>

  <input type="text" onkeydown="displayResult()">

</body>
</html>
        